Forecasting Methods
There are several different methods that can be used to create a forecast. The method forecaster chooses depends upon the experience of the forecaster, the amount of information available to the forecaster, the level of difficulty that the forecast situation presents, and the degree of accuracy or confidence needed in the forecast.
The first of these methods is the persistence method;the simplest way of producing a forecast. The persistence method assumes that the conditions at the time of the forecast will not change. For example, if it is sunny and 87 degree today, the persistence method predicts that it will be sunny and 87 degree tomorrow. If two inches of rain fell today, the persistence method would predict two inches of rain for tomorrow. However, if weather conditions change significantly from day to day, the persistence method usually breaks down and is not the best forecasting method to use.
The trends method involves determining the speed and direction of movement for fronts, high and low pressure centers, and areas of clouds and precipitation. Using this information, the forecaster can predict where he or she expects those features to be at some future time. For example, if a storm system is 1,000 miles west of your location and moving to the east at 250 miles per day, suing the trends method you would predict it to arrive in your area in 4 days. The trends method works well when systems continue to move at the same speed in the same direction for a long period of time. if they slow down, speed up, change intensity, or change direction, the trends forecast will probably not work as well.
The climatology method is another simple way of producing a forecast. This method involves averaging weather statistics accumulated over man years to make the forecast. For example, if you were using the climatology method to predict the weather for new York City on July 4th, you would go through all the weather data that has been recorded for every July 4th and take an average. The climatology method only works well when the weather pattern is similar to that expected for the chosen time of year. if the pattern is quite unusual for the given time of year, the climatology method will often fail.
The analog method is a slightly more complicated method of producing a forecast. It involves examining today's forecast scenario and remembering a day in the past when the weather scenario looked very similar (an analog). The forecaster would predict that the weather in this forecast will behave the same as it did in the past. The analog method is difficult to use because it is virtually impossible to find a predict analog. Various weather features rarely align themselves in the same locations they were in the previous time. Even small differences between the current time and the analog can lead to very different results.
31 What factor is NOT mentioned in choosing a forecasting method? __________
A Imagination of the forecaster.
B Necessary amount of information.
C Practical knowledge of the forecaster.
D Degree of difficulty involved in forecasting.
32 Persistence method will work well __________.
A if weather conditions change greatly from day to day
B if weather conditions do not change much
C on sunny days
D on rainy days
33 The limitation of the trends method is the same as the persistence method in that __________.
A it makes predications about weather
B it makes predications about precipitation
C the weather features need to be well defined
D the weather features need to be constant for a long period of time
34 Which method may involve historical weather data? __________
A The trends method.
B The analog method.
C Both climatology method and analog method.
D The trends method and the persistence method.
35 It will be impossible to make weather forecast using the analog method __________.
A when the current weather scenario differs from the analog
B when the current weather scenario is the same as the analog
C when the analog is over ten years old
D when the analog is a simple repetition of the current weather scenario
31 A第一段第二句說(shuō)明了選擇預(yù)報(bào)方法應(yīng)考慮的一些因素，其中包括B、C和D中提到的所能獲得的信息、預(yù)報(bào)者的實(shí)際經(jīng)驗(yàn)和特定天氣狀況給預(yù)報(bào)造成的困難程度。A是正確的選項(xiàng)，因?yàn)槲闹形刺岬教鞖忸A(yù)報(bào)員的想象力。
32 B答案可在第二段第二句中直接找到，其后是具體例子，用于說(shuō)明persistence method只有在天氣狀況基本不變的情況下才能有效使用。
33 D第三段最后兩句提供了答案。另外，該題的理解還須結(jié)合對(duì)第二段的理解。
34 C第四段的第二句告訴我們，the climatology method需要取多年積累起來(lái)的氣象數(shù)據(jù)的平均值。第三句提供了具體例子。第五段的第二句和第三句說(shuō)明，analog method也需要比較和對(duì)比歷某一天的氣象狀況。
35 A最后一段的第五句和第六句提供了答案。
There are several different methods that can be used to create a forecast. The method forecaster chooses depends upon the experience of the forecaster, the amount of information available to the forecaster, the level of difficulty that the forecast situation presents, and the degree of accuracy or confidence needed in the forecast.
The first of these methods is the persistence method;the simplest way of producing a forecast. The persistence method assumes that the conditions at the time of the forecast will not change. For example, if it is sunny and 87 degree today, the persistence method predicts that it will be sunny and 87 degree tomorrow. If two inches of rain fell today, the persistence method would predict two inches of rain for tomorrow. However, if weather conditions change significantly from day to day, the persistence method usually breaks down and is not the best forecasting method to use.
The trends method involves determining the speed and direction of movement for fronts, high and low pressure centers, and areas of clouds and precipitation. Using this information, the forecaster can predict where he or she expects those features to be at some future time. For example, if a storm system is 1,000 miles west of your location and moving to the east at 250 miles per day, suing the trends method you would predict it to arrive in your area in 4 days. The trends method works well when systems continue to move at the same speed in the same direction for a long period of time. if they slow down, speed up, change intensity, or change direction, the trends forecast will probably not work as well.
The climatology method is another simple way of producing a forecast. This method involves averaging weather statistics accumulated over man years to make the forecast. For example, if you were using the climatology method to predict the weather for new York City on July 4th, you would go through all the weather data that has been recorded for every July 4th and take an average. The climatology method only works well when the weather pattern is similar to that expected for the chosen time of year. if the pattern is quite unusual for the given time of year, the climatology method will often fail.
The analog method is a slightly more complicated method of producing a forecast. It involves examining today's forecast scenario and remembering a day in the past when the weather scenario looked very similar (an analog). The forecaster would predict that the weather in this forecast will behave the same as it did in the past. The analog method is difficult to use because it is virtually impossible to find a predict analog. Various weather features rarely align themselves in the same locations they were in the previous time. Even small differences between the current time and the analog can lead to very different results.
31 What factor is NOT mentioned in choosing a forecasting method? __________
A Imagination of the forecaster.
B Necessary amount of information.
C Practical knowledge of the forecaster.
D Degree of difficulty involved in forecasting.
32 Persistence method will work well __________.
A if weather conditions change greatly from day to day
B if weather conditions do not change much
C on sunny days
D on rainy days
33 The limitation of the trends method is the same as the persistence method in that __________.
A it makes predications about weather
B it makes predications about precipitation
C the weather features need to be well defined
D the weather features need to be constant for a long period of time
34 Which method may involve historical weather data? __________
A The trends method.
B The analog method.
C Both climatology method and analog method.
D The trends method and the persistence method.
35 It will be impossible to make weather forecast using the analog method __________.
A when the current weather scenario differs from the analog
B when the current weather scenario is the same as the analog
C when the analog is over ten years old
D when the analog is a simple repetition of the current weather scenario
31 A第一段第二句說(shuō)明了選擇預(yù)報(bào)方法應(yīng)考慮的一些因素，其中包括B、C和D中提到的所能獲得的信息、預(yù)報(bào)者的實(shí)際經(jīng)驗(yàn)和特定天氣狀況給預(yù)報(bào)造成的困難程度。A是正確的選項(xiàng)，因?yàn)槲闹形刺岬教鞖忸A(yù)報(bào)員的想象力。
32 B答案可在第二段第二句中直接找到，其后是具體例子，用于說(shuō)明persistence method只有在天氣狀況基本不變的情況下才能有效使用。
33 D第三段最后兩句提供了答案。另外，該題的理解還須結(jié)合對(duì)第二段的理解。
34 C第四段的第二句告訴我們，the climatology method需要取多年積累起來(lái)的氣象數(shù)據(jù)的平均值。第三句提供了具體例子。第五段的第二句和第三句說(shuō)明，analog method也需要比較和對(duì)比歷某一天的氣象狀況。
35 A最后一段的第五句和第六句提供了答案。